The group was believed to be travelling to an official ceremony in the northeastern province of Xiangkhouang on an air force jet manufactured by Ukraine's Antonov.
Lao Defence Minister Douangchay Phichit was among five senior officials killed in the crash, the permanent secretary of the Thai defence ministry, Nipat Thonglek, told AFP.
He said that he had been informed of the deaths by a senior Lao military official and would attend the defence minister's funeral on behalf of Thailand.
The foreign ministry in Bangkok said about 20 people were on board including the Vientiane governor and other prominent figures.
The official Lao news agency KPL confirmed the crash and said the authorities were trying to rescue survivors.
It said the accident involved an Antonov AN-74TK-300 plane operated by the Lao air force - but did not give any information about the passengers or any casualties.
"The authority concern is now helping to rescue the survivors," it said in a brief English-language report.
"The cause of accident is under the investigation."
The news agency showed pictures of the wreckage of the plane in the Lao jungle.
Laos has had 30 fatal air accidents since the 1950s, according to the Aviation Safety Network.
In October last year a civilian airplane operated by Lao Airlines plunged into the Mekong River in bad weather killing all 49 people on board.
The landlocked country of about seven million people has an authoritarian one-party government and is one of Asia's poorest nations.
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